Using a place holder to add a drive later on.

[dcrichter]

Ive been doing gobs of reading on all sorts of nas systems and my familiarity with linux is average for a networking guy, but when it comes to freenas im a complete noob.

My wants - Have a 20 sata drive storage array for storing movies, I would not fill this right away however. I would use a combination of sata controllers and sata multipliers for connectivity and supporting MB,proc and ram with a dedicated OS drive. Looking to use a ZFS storage system with as large of percentage of usable space as possible while still keeping with 2 drive failure redundancy. All systems accessing the NAS would need to see this as one large drive.
1. Data survivability - drive failure to the point of 2 drives could fail without loss
2. Replacement of smaller drives with larger drives - would like this to occur with system live but it could go down for this.
3. Addition of drives overtime
This is to handle mainly video storage for my home media system.

All of my wishes and then some I know can be met by freenas except the last.

Adding drives is the issue though - Ive seen some work a-rounds to this and the best i seem to find is the ability to add additional arrays to the overall pool - this however lessens the percentage of usable space.

MY big question - Is it possible to us some sort of "place holder" drive that could be later replaced with an actual drive connected to the sata bus of my system? This "place holder" could be a series of partitions, virtual drives, worst case even a number of usb drives.

THis is what im thinking - 1x 750gb, 2x 1TB, 1x 2TB and 1x 1TB split into 16 roughly 125 GB partitions. The 125GB partitions could then be replaced over time with a physical drive. essentially you would remove 1 125gb partition and add the new drive in its place.

I tried to find anything that eluded to this setup in the forums but to no avail.

Please help, Thanks!

 

[Letni]

Assuming you would be creating "1" pool of all 16 x 125 GB partitions, you would be putting yourself at great risk.. Lets just say that you have your 1 x 750 GB drive fail and you have 6 x 125 GB partitions defined as individual "devs" within a raidz2 or even raidz3. In essence you would be incuring 6 instant drive failures within your pool immediately losing your zpool since even with raidz3 you could at most lose 3.

 

[ProtoSD]

And in addition to what Letni said, for optimal ZFS performance, you should break your pool up into vdevs of 8 disks for raidz2 (or even numbers or disks in each vdev).

You placeholder proposal is not impossible, but not for a noob, and there are so many things that can go wrong unless you really really really know how things work it's not even worth the time to try and explain how. Also, FreeNAS isn't fond of having partitions in different pools/vdevs. If you value your video collection/data as much as I do, I wouldn't even think twice about it. ZFS is designed to have disks added to pools as vdevs, this isn't a workaround, this is how ZFS works.

You just have learn to accept the way ZFS works or accept some other inferior storage solution. ;)

 

[dcrichter]

Thanks for the insight from both of you, It appears I overlooked a few issues of what this would entail and the issues that could arise.

protosd, since you have a video collection and thats my main point of this system with 20 drives would it be advisable to split them up into say 8, 8 and 4 drive vdevs? In this way i could use my current set of 3x 1TB and 1x750GB drives in the smaller vdev and as storage becomes needed build out the other 2 vdevs to add to the pool. Also could you point me to any reading that would be helpful and any thoughts or tricks you have found dealing with video storage. Currently im at the 3TB full of movies and the risk of loss is a bit unnerving.

Thanks again for dealing with a noob at this.